Photomechanical printing process and printing material for carrying out the same



Patented June 20, 1.944

PHOTOMECHANIOAL PRINTING PROCESS" AND PRINTING MATERIAL FOR GARRY- INGOUT THE SAME Andr Rott, Berchem-Antwerp, Belgium; vested in the AlienProperty, Custodian No Drawing. Application July 21, 1941,

. Serial No. 403,392-

8 Claims.

The present invention relates to a photo-meand the print is produced byexposing such lightsensitive printing materials through a masterimageand thereafter developing and fixing the print in the usual manner.

It has now been found that a photographic image produced in a silverhalide layer can be made to produce a reversed imag on an inertmaterial, i. e. a material which is not sensitive to light, providedthesilver halide layer, after being exposed to light for the productionof a master image and then being impregnated with a developer to developthis image, is pressed or squeezed, in the presence of a fogging agentand. x

a silver halide solvent, onto an inert printing material (receptionmaterial) while the layer is still imbibed with the developing liquid.If this is done, that part of the silver halide in the layer which wasnot reduced during the exposure to light and which in the ordinaryphotographic process would be fixed out in the fixing bath, will adhereto and, if the reception material is porous, will enter this material bydiffusion and will produce thereon a reversed image. In order to renderthis image freely visible, the light sensitive layer containing themaster image will normally be removed from the reception material.

Fogging agents are known to be substances capable of promoting thereduction of silver halides without requiring for this the action oflight. Of these substances there may be mentioned by way of example:colloidal silver, colloidal forms of sulfur, silver sulfites,hypophosphites, stannous chloride and organic sulfur compounds, whichare capable of splitting off sulfur in the form of a bivalent ion. Oneof these latter compounds is thiosinamine.

Ithas been found that the presence of substances 'suchas referred to inthe foregoing will improve and acceleratethe transfer process. To benoted is the fact thatthese substances may belong to the class ofproducts whichact as reduction nuclei or crystallization nuclei forsilver halides, as for example colloidal silver, silver sul phide,colloidal sulphur, phosphorous, or to the class of substances which arenot such nuclei themselves but may form such nuclei by interaction withthe diffusing silver halides, either by reduction as in the instance ofstannous chloride or by the formation with the silver halides ofdiflicultly soluble compounds such as sulphides or organic substanceswhich easily split off sulphur as for instance thiosinamine.

The silver halide solvents contained in the usual photographicdevelopers such as sodium sulphite, suffice, but also special solventsmay be added. Sodium thiosulfate, which is a silver halide solvent, actsalso as a fogging agent by promoting the reduction of the halideswithout requiring the action of light.

The fogging agent is preferably incorporated in the reception materialeither during the manufacture of the latter or by impregnation of thefinished material. I v

The expression reception material as used throughout this specificationand in the appended claims is to be understood as the material on whichthe image is finally deposited according to this invention.

Furthermore, it has proved to be useful to fix the active substances inthe reception material by means of precipitants (for instance sodiumthiosulphate may be precipitated by barium chloride) As receptionmaterials there may b used coated and uncoated paper, multilayered orstripping supports, textiles, wood, Celluloid and other plastics, metal,glass, porcelain and many other materials which may not be suited forthe normal photographic process.

The process according to the present invention is particularly useful inthe transfer of images onto both sides of a sheet formed carrier, whichis of great importanc in the reproduction of documents and books;wherein it offers the advantage of avoiding the risk incurred with amaterial coated with light sensitive layers on both sides, but being notsufficiently impervious to light to prevent the light rays used forprinting from affecting the opposite sensitive layer.

The photographic images obtained by transfer according to this processconsist of very finely divided silver and silver compounds. They areaccessible to any of th subsequent treatments employed in photography,such as intensification, reduction, toning, colouring by dye mordantingprocesses or colour development and may also be used in contact-tanningreactions like ordinary photographic images. They may be used forbuilding up colour images by the silver bleaching process.

any subsequent treatment the developed image'is pressed onto a textilesupport and kept in/contact with it for 10 minutes. After stripping the"photographic paper, a positive image remains on the textile support.

For the purpose of obtaining the same design in colour, it is bleachedin a bath containing 5 g. potassium ferricyanide and 5 g. potassiumbromide per liter, then washed and developed in a known colourdeveloper, containing as a colour coupler trichloro-a1pha-naphthene.A'blue image is obtained by this treatment.

Example 2.-In the production of a reception material 100 ccms. of agelatine solution of 1% are mixed with com. silver nitrate, 10% and 1com. hydroquinone 1% are added. ccms. of the colloidal silver'sol formedare mixed with a solution of 60 g. gelatine and l g. sodium thiosulfatein one liter water. This mixture is cast on a paper support.

From a photographic diapositive an enlargement is made on silver bromidepaper and developed in a paramethylamido hydroxybenzene hydroquinonedeveloper and to which 1 g. sodium thiosulphate is added per litre.After development, the image, without having been Washed, is squeezedonto the reception material, which during development in order topromote the reaction has already been treated with the developertogether with the silver bromide paper. After 10 minutes the two layersare separated. An enlarged positive image remains on the receptionmaterial and it may be treated subsequently in a selenium toning bath soas to enhance the toning.

Example 3.In the production of another reception material 1 liter of a10% gelatine solution is mixed with 100 ccms. of a 0.1% sodium sulfidesolution and 200 ccms. of a 0.1% silver nitrate solution. The mixture isheated one hour at 40-45 C. and after solidification is shredded, washedand after melting, cast onto a paper support and dried. This materialmay be used in ously in the same bath so as to promote the proceeding.After th exposure and development of the refiectographic paper sheetsare pressed onsided positive copy and after washing no further thetransfer of images as described with reference to Example 2.

Example 4.In order to produce a. reception material two mixtures areprepared viz. a solution A, containing, 100 g. gelatine and 150 g.bariumchloride in 1 liter water and a solution B, containing 100 g.gelatine and 150 g. sodium thiosulfate in 1 liter water. The solutionsare mixed at a temperature of C. and the solidified mixture is shredded,washed again and after remelting mixed with an equa1 quantity of 0.1%sodium sulfide solution. The mixture is cast onto a paper support anddried. A similar mixture is cast on the backside of the support anddried.

On two sheets of silver halide paper a print is made refiectographicallyof each side of a doublesided printed document. The two sheets aredeveloped for one minute in a usual paramethylamido hydroxybenzenehydroquinone developer, the reception material being treatedsimultanetreatmefitis" required.-

7 Example 5.In the manufacture of a reception material a solutioncomprising 1 liter gelatine 6%, 30 com, of a 0.2% thiosinamine solutionand 20 com. of a 10% sodium thiosulphate solution are cast on amultilayered support of medium thickness which includes a strippinglayer and a thin paperlayer.

A sheet of silver halide is exposed reflectographically and developedone minute in a hydroquinone development. At the same time the receptionmaterial is treated in the same bath. After development both layers arepressed upon one another and after ten minutes are separated. Thepositive thus obtained may be stripped after washing and drying. Thismethod of transfer is particularly suitable for use in air mailcorrespondence.

Example 6.On a paper support, provided with a stripping gelatine layer,a mixture consisting of 50 g. gelatine, 3 g. sodium thiosulphate and 0.3g. stannous chloride are cast and dried.

The treatment of this material for image transfer is the same asdescribed with reference to Example 5. After washing and drying, thethick gelatine layer may be stripped. There remains a diapositive of thetext which may be used further according to known photomechanicalprocesses. Various changes may be made in the details disclosed in theforegoing specification without departing from the invention orsacrificing the advantages thereof.

I claim:

1. The process of photographic image transfer which comprises contactinga photographic silver halide layer containing a developing solution anda developed photographic image in the presence of a silver halidesolvent and a fogging agent with a reception material which isinsensitive to light.

2. The process of claim 1, in which the fogging agent is a colloidalprecious metal compound,

3. The process of claim 1, in which the fogging agent is a sulfurcontaining substance capable of splitting off sulfur in the form ofbivalent ions.

4. The process of claim 1, in which the fogging agent is a tin compoundcapable of splitting off in an alkaline medium stannous ions.

5. The process of claim 1, in which sodium thiosulfate is present to actboth as a silver halide solvent and a fogging agent.

6. A reception material adapted for use in the process of claim 1consisting of a material insensitive to light and which containsstannous chloride as a fogging agent.

7. A reception material adapted for use in the process of claim 1consisting of a material insensitive to light and which containsthiosinamine as a fog ing agent.

ANDRE. Borr-

